The Supreme Court raised concerns Monday over the constitutionality of President Obama's use of his authority to make appointments when Congress is away on break.

The case, an offshoot of a bitter partisan dispute on Capitol Hill, has broad implications regarding when and how presidents can use a constitutional provision to bypass Congress and directly appoint candidates to high-level posts.

This is not the horse-and-buggy era anymore.

Justices heard arguments for about 90 minutes -- 30 minutes longer than normal -- for National labor Relations Board v. Noel Canning, which calls into question three appointments Obama made to the five-member panel Jan. 4, 2012. Congress was on break at the time after opening its annual session a day earlier.

Presidents can circumvent required Senate approval if the chamber is on recess, a move Obama deemed necessary because of repeated Republican blocks of his nominations to the panel.

But the White House and Senate Republicans are at odds over the definition of "recess." The administration argues a recess applies to breaks between annual sessions as well as time off Congress takes within the year. But Republicans say the term should only apply to breaks between official sessions of Congress.

The high court also must decide two other questions: whether a president's recess-appointment power extends to any vacancy that exists or only those vacancies that occur during the recess; and whether brief, "pro forma" sessions of the Senate -- held every few days to break up a longer Senate hiatus-- can prevent the president from making recess appointments.

The administration must win on all three accounts to settle its debate with Capitol Hill Republicans.

Solicitor General Donald Verrilli Jr., arguing the case on behalf of the Obama administration, warned that ruling against the NLRB would cast a legal cloud over hundreds of rulings by the board, which resolves complaints of unfair labor practices and conducts elections for labor union representation.

But some justices suggested the Constitution's framers may have intended for recess appointments to be used to fill vacancies when travel concerns meant that Congress wasn't in session for long periods of time — not as a way for presidents to bypass a Senate that didn't approve of his nominees.

Justice Elena Kagan questioned whether most modern-era presidents of both parties have used recess appointments "as a way to deal -- not with congressional absence -- but with congressional intransigence, with a Congress that simply does not want to approve appointments that the president thinks ought to be approved."

"This is not the horse-and-buggy era anymore," Kagan said.

Justice Antonin Scalia said that if Obama deemed the NLRB appointments an emergency that warranted immediate attention, then he had the constitutional authority to call the Senate back into session to deal with the issue.

"So what's the problem?" Scalia asked Verrilli. "If there is indeed this, you know, this terrible emergency you're talking about, the president has the power to call them back."

The solicitor general answered that the Constitution's farmers gave the president the power to both call Congress back for emergency sessions and make recess appointments, and that the two issues aren't mutually exclusive.

Justice Anthony Kennedy said that since every two-year Congress is divided into year-long "first" and "second" sessions -- terms the body itself uses -- "why don't we defer to Congress as to what the term 'session' means and say that this gives us guidance as to when there is a recess?"

"There is a recess between those sessions," said Kennedy, suggesting that recesses occur only in between annual sessions.

The Supreme Court case involves a dispute between Noel Canning (part of Noel Corp.), of Yakima, Wash., and the Teamsters union. The NLRB ruled against Canning, and the company sued, arguing the president's January 2012 appointments to the board were invalid and thus the panel didn't have the necessary quorum to resolve its dispute.

The U.S. Court of Appeals for the District of Columbia Circuit ruled in favor of Canning, saying Obama violated the law when he bypassed the Senate.

The NLRB appealed, and the Supreme Court took up the case.

Recent changes in the Senate's filibuster rules mean that most presidential nominations now only need a simple majority to clear procedural hurdles and head toward a final simple majority passage in the 100-member chamber, not the 60 votes previously required to block a nominee.

But if the high court rules against the labor board, a minimum of 100 NRLB decisions — and possibly more — made by the recess-appointed members could be deemed invalid.